The invention relates to a tool for metal machining bore surfaces with at least two component tools that can be displaced with respect to each other, in accordance with the main concept of claim 1.
Tools of the type addressed here are known. Their purpose is to machine at least two bore surfaces within a workpiece, for example, the surfaces for the valve seat and for the valve stem guide inside the cylinder head of an internal combustion engine (DE 44 31 149 A1). In the case of the known tool, the relative movement of the component tools in the axial direction is brought about by means of an external drive. This leads to a very costly and space-intensive construction of the driving arrangement.
For this reason, it is the task of the invention to create a tool of the initially mentioned type, which does not have these disadvantages and which distinguishes itself by having a very compact construction.
To reach this objective, a tool is proposed which comprises the characteristics as described and claimed herein. The tool distinguishes itself in that it has a primary piston that, for the purpose of producing an extension movement of the inner component tool, can be charged with a certain medium under pressure. During an extension movement, brought about by the medium, the primary piston displaces a medium via another! connection channel into an equalizing space, arranged concentrically about the axis of rotation of the tool and being in the form of an annular chamber. Inside this annular chamber, an annular compensating piston is movably arranged, this is also displaced during movement of the primary piston. Due to the annular shape of the compensating piston, it is possible to build the tool with the two pistons being very short and compact, which is very advantageous particularly during use in automatic processing stations. Hence, the shorter the tool structures, the more precise are the processed bores.